This invention is directed to acrylic device materials. In particular, this invention relates to soft, high refractive index acrylic device materials particularly suited for use as intraocular lens (xe2x80x9cIOLxe2x80x9d) materials.
With the recent advances in small-incision cataract surgery, increased emphasis has been placed on developing soft, foldable materials suitable for use in artificial lenses. In general, these materials fall into one of three categories: hydrogels, silicones, and acrylics.
In general, hydrogel materials have a relatively low refractive index, making them less desirable than other materials because of the thicker lens optic necessary to achieve a given refractive power. Silicone materials generally have a higher refractive index than hydrogels, but tend to unfold explosively after being placed in the eye in a folded position. Explosive unfolding can potentially damage the corneal endothelium and/or rupture the natural lens capsule. Acrylic materials are desirable because they typically have a high refractive index and unfold more slowly or controllably than silicone materials.
U.S. Pat. No. 5,290,892 discloses high refractive index, acrylic materials suitable for use as an IOL material. These acrylic materials contain, as principal components, two aryl acrylic monomers. They also contain a cross-linking component. The IOLs made of these acrylic materials can be rolled or folded for insertion through small incisions.
U.S. Pat. No. 5,331,073 also discloses soft acrylic IOL materials. These materials contain as principal components, two acrylic monomers which are defined by the properties of their respective homopolymers. The first monomer is defined as one in which its homopolymer has a refractive index of at least about 1.50. The second monomer is defined as one in which its homopolymer has a glass transition temperature less than about 22xc2x0 C. These IOL materials also contain a cross-linking component. Additionally, these materials may optionally contain a fourth constituent, different from the first three constituents, which is derived from a hydrophilic monomer. These materials preferably have a total of less than about 15% by weight of a hydrophilic component.
U.S. Pat. No. 5,693,095 discloses foldable ophthalmic lens materials comprising a total of at least 90% by weight of only two principal lens-forming monomers. One lens-forming monomer is an aryl acrylic hydrophobic monomer. The other lens-forming monomer is a hydrophilic monomer. The lens materials also comprise a cross-linking monomer and optionally comprise a UV absorber, polymerization initiators, reactive UV absorbers and reactive blue-light absorbers.
Improved soft, foldable acrylic materials which are particularly suited for use as IOLs, but which are also useful as other ophthalmic or otorhinoloaryngological devices, such as contact lenses, keratoprostheses, corneal rings or inlays, otological ventilation tubes and nasal implants have now been discovered. These materials contain only one principal lens-forming component: an aryl acrylic hydrophobic monomer. The materials of the present invention comprise at least about 80% by weight of the principal monomeric component. The remainder of the material comprises a cross-linking monomer and optionally one or more additional components selected from the group consisting of UV-light absorbing compounds and blue-light absorbing compounds.
Among other factors, the present invention is based on the finding that acrylic copolymers suitable for use as foldable IOL materials can be synthesized using only one principal aryl acrylic hydrophobic monomer, reducing or eliminating difficulties, such as physico/chemical heterogeneity, associated with curing copolymers that contain two or more principal device-forming monomers.